An optical interface cable (optical IF cable) has been recently used as a transmission medium in order to achieve a higher transmission speed. Network equipment, which is connected by the optical IF cable and provided with an optical interface (optical IF), is liable to increase power consumption due to transmission or reception of an optical signal.
In view of this, in one example, Patent Literature 1 discloses a technique of reducing power consumption by performing modulation and outputting at a level that does not cause trouble in communication depending on transmission data. In addition, Patent Literature 2 discloses a technique of reducing power consumption by performing transition between four states of active, idle, passive, and off.